Shielding

[ognolman]

Ok, first off, let me say that I have done the copper tape shielding bit several times and I think I do a pretty nice job of it.  My Warmoth G5 Korina was carefully and neatly shielded with copper tape and I don't think it will ever be an issue.  I was quite proud of the job I did, in fact. 

However, my Warmoth Jazz (The SeaFoam jazz in the completed section) is not shielded at all, on the advice of a local luthier and electronics wizard.  He sent me this link from his website to back up his advice:

http://www.darrenriley.com/OntheBench.htm

He talked me out of the shielding on that bass, and I've been playing it live and recording with it for about a year now with no problems at all.  It's quiet as can be.  (It has a Bartolini preamp.)

I asked him if I should shield it with that grey paint-on stuff and he said that the grey stuff is very nasty to work with, even toxic, IIRC.  He said to just leave it unshielded, that there is no difference in sound quality.

So what is the big deal about shielding these things?  I think my luthier is right--doesn't seem to make a difference to me.  Why are we wasting our time?

JBD

 

[TRG]

GOOD TO KNOW :cool01:

 

[SkuttleFunk]

what pickups (brand, model, and type) did you use? it could be that your specific choice of pickups and pre-amp eliminated the need for "additional" shielding ... I suspect you might be utilizing EMG active (battery powered) pickups, and not the typical passive single-coil pickups most people utilize

shielding is a good thing, and something a competent Luthier (or even a compitent builder/assembler) should know the benefits of. I am very surprised that they argued against shielding.

all the best,

R

 

[ognolman]

what pickups (brand, model, and type) did you use? it could be that your specific choice of pickups and pre-amp eliminated the need for "additional" shielding ... I suspect you might be utilizing EMG active (battery powered) pickups, and not the typical passive single-coil pickups most people utilize

It was a Bartolini preamp and Bartolini passive dual coil Jazz pickups in that particular bass.

I have another Jazz bass that I'm working on now that has a single coil neck Jazz and dual coil MM bridge, both Barts with an Audere preamp.  No shielding and dead quiet unless I boost the treble all the way, but that just gives hiss from too much treble boost.

shielding is a good thing, and something a competent Luthier (or even a compitent builder/assembler) should know the benefits of. I am very surprised that they argued against shielding.

He is a very competant builder and luthier, one of the most highly respected in the area, in fact.  He's the go-to guy when it comes to electronics repair in this area and he's done work for some major acts.  I'll have to admit that the strat in the link I provided was a mess, but it looked to me like it was originally a very amaturish job to begin with.  I imagine that he deals with a lot of amature foil jobs, which undoubtedly colors his opinions.  Looking at the sheer quantity of foil used on that guitar its no wonder it was having problems.  I honestly think that in my basses it would never get that messed up because there's not that much foil, even when I've lined the pickup and control cavities.

I'm inclined to keep doing it just because if I go to sell it everyone wants to see shielding or they think it is cursed.

JBD

 

[chuck7]

I think a lot depends on your environment.  If you are in a RF quite environment, there isn't much noise to be picked up by the electronics.  Also, if you used a coax (braided shielding over lead) wire, thats going to go along way towards giving you shielding. 

 

[dbw]

You said they were dual coil pups... those are hum-canceling.  Plus it's a Jazz bass... the control plate makes for a good shield even without any foil.

 

[jackthehack]

I you search back through old posts (it might have been on the old board) a while back I did some extensive experimentation with a Strat body in a high $$$ RF isolation chamber I have access to at work, and either the shielding tape as sold for guitars (there's much higher value RF tape unavailable to consumers) or the StewMac type shielding tape have an effect that is at best negligible when tested under scientific conditions.

In an RF free environment, there is 0 effect on the ambient amount of "hum" at max volume on the guitar and a Fender Blues Deluxe typical of single coil pickups (Fender Custom Shop '69s). With induced sources of typical RF (electric fan/poorly shielded laptop/fluorescent light fixture) reduction in audible "hum" was at best 1.5-2 dB, which is pretty negligible.

So, if it floats your boat, shield away with paint or tape, but the overall efficacy is near nil. You're better off ensuring your ground circuit is as good as it can be, using high quality pots, purchasing high quality shielded cabling, and eliminating RF producing sources (fans/electric motors/fluorescent lighting/poorly shielded computers and other electronics from the environment.

 

[ognolman]

I you search back through old posts (it might have been on the old board) a while back I did some extensive experimentation with a Strat body in a high $$$ RF isolation chamber I have access to at work, and either the shielding tape as sold for guitars (there's much higher value RF tape unavailable to consumers) or the StewMac type shielding tape have an effect that is at best negligible when tested under scientific conditions.

In an RF free environment, there is 0 effect on the ambient amount of "hum" at max volume on the guitar and a Fender Blues Deluxe typical of single coil pickups (Fender Custom Shop '69s). With induced sources of typical RF (electric fan/poorly shielded laptop/fluorescent light fixture) reduction in audible "hum" was at best 1.5-2 dB, which is pretty negligible.

So, if it floats your boat, shield away with paint or tape, but the overall efficacy is near nil. You're better off ensuring your ground circuit is as good as it can be, using high quality pots, purchasing high quality shielded cabling, and eliminating RF producing sources (fans/electric motors/fluorescent lighting/poorly shielded computers and other electronics from the environment.

Well said, Jack.  And thanks for doing the legwork on that!  It's pretty difficult to argue with a combination of rigorous scientific data and real-world experience when they both seem to arrive at the same conclusion.

JBD

 

[ByteFrenzy]

Did you manage to do any testing with higher qualities of shielding tape or a cavity shield from real foil? I'm not so sure these would fare much better with all the wires running through (PU leads, output cable, maybe battery wires). In secure shielded environments (anti-eavesdropping) only optical in-out or, if absolutely unavoidable, special shielded cables are permitted to enter/leave.

 

[ognolman]

I you search back through old posts (it might have been on the old board) a while back I did some extensive experimentation with a Strat body in a high $$$ RF isolation chamber I have access to at work, and either the shielding tape as sold for guitars (there's much higher value RF tape unavailable to consumers) or the StewMac type shielding tape have an effect that is at best negligible when tested under scientific conditions.

I did a search but couldn't find the old post.

One thing of note here is that the lugs on pots and switches are totally uninsulated.  I've never seen a pot or switch on a guitar that had any kind of insulation where the wire connects.  So if there was any place that was really vulnerable to RFI it would be at those solder joints.  Obviously, this doesn't seem to be a problem, though.

JBD

 

[jackthehack]

"Did you manage to do any testing with higher qualities of shielding tape or a cavity shield from real foil? I'm not so sure these would fare much better with all the wires running through (PU leads, output cable, maybe battery wires). In secure shielded environments (anti-eavesdropping) only optical in-out or, if absolutely unavoidable, special shielded cables are permitted to enter/leave."

No; I only have access to small pieces or the shielding tape precut to fit inside sections of cell phones and an extremely limited supply of pieces about 3"x5". The paint is only kept in factory and some overseas testing facilities and is extremely high $$$.  An RF isolation chamber is pretty much the equivalent of a tempested facility.

"I did a search but couldn't find the old post. One thing of note here is that the lugs on pots and switches are totally uninsulated.  I've never seen a pot or switch on a guitar that had any kind of insulation where the wire connects.  So if there was any place that was really vulnerable to RFI it would be at those solder joints."

May have been on the old board. Faulty logic on the lug, the whole pot is unshielded. A poor/bad solder join at any grounding point will cause a lot more hum/noise than almost all ambient RF.

 

[Patrick from Davis]

The ground solder joint to the back of the pot makes the metal case of the pot a shield.  The solder joint where the "live" wire goes to the pot is not shielded, but it is a very short distance.  It was described to me as the length of unshielded wire more or less equals the size of the noise antenna, if you will.  Shielded wire, and proper soldering/grounding on passive pick up instruments should be all that is required.  On active instruments, you do have a preamp, and more wire distance.  The preamp will boost any noise you pick up.  I can see where shielding the enclosure of an active preamp on a guitar/bass would be helpful to limit stray noise.
Patrick

 

[Orpheo]

I you search back through old posts (it might have been on the old board) a while back I did some extensive experimentation with a Strat body in a high $$$ RF isolation chamber I have access to at work, and either the shielding tape as sold for guitars (there's much higher value RF tape unavailable to consumers) or the StewMac type shielding tape have an effect that is at best negligible when tested under scientific conditions.

In an RF free environment, there is 0 effect on the ambient amount of "hum" at max volume on the guitar and a Fender Blues Deluxe typical of single coil pickups (Fender Custom Shop '69s). With induced sources of typical RF (electric fan/poorly shielded laptop/fluorescent light fixture) reduction in audible "hum" was at best 1.5-2 dB, which is pretty negligible.

So, if it floats your boat, shield away with paint or tape, but the overall efficacy is near nil. You're better off ensuring your ground circuit is as good as it can be, using high quality pots, purchasing high quality shielded cabling, and eliminating RF producing sources (fans/electric motors/fluorescent lighting/poorly shielded computers and other electronics from the environment.

thank you, you just confirmed the ideas I had all along. in fact, I think shielding attenuates a bit of the highs! (its one big capacitor after all!) and thats something I surely dont like. not on a fender, not on a gibson.

 

[ognolman]

On active instruments, you do have a preamp, and more wire distance.  The preamp will boost any noise you pick up.  I can see where shielding the enclosure of an active preamp on a guitar/bass would be helpful to limit stray noise.

I understand this is the primary reason why active on-board preamps exist.  Because the distance between the pickup and the preamp is so short there is little chance for any stray noise to be boosted.  Put the preamp at the end of a 20' guitar cable and it is much more likely to amplify unwanted signals.

JBD

 

[Patrick from Davis]

The guitar cord is shielded.  The wire distance I was talking about is not the distance from the pick up to the preamp, but the total distance of the traces in the preamp.  For instance, in a very simple passive design, the signal goes from the pick up to the volume knob to the output jack.  More or less a linear distance from the pick up to the output jack.  In an active design, the active line goes from the pick up into the electronics, where there is a mess of electronics that make the distance the signal goes much longer.  This increases the amount of antenna available.  Probably more of a problem is that several of the components tend to pick up noise at a greater rate than the wire, but I don't know how to measure that consistently.  Resister are culprits, the DIY amp folks talk a lot about them.  And pots are just resisters that...

The guitar cord is shielded.  It is a braided ground surrounding the signal cord in the middle.  The capacitance of this cable is a valid point.  Bill Lawrence talks a bit about it on his site if you can find a way to the cables he sells.  He mentions that those old coiled cords had a particular capacitance value and that this was a part of Hendrix's tone.  But, you can get the low capacitance cord from him, or George L, and then add in the electronics later to mimic the old cables.  You can also talk to Bill about this kind of stuff, but according to CB you head will start spinning very quickly. 
Patrick

 

[ByteFrenzy]

The guitar cord may be shielded, but since it is asymmetrical it will still pick up a significant amount of interference as it gets longer. That is one of the main reasons why you should keep instrument cables as short as possible, and if you need to cover a greater distance, use a DI box close to the instrument and cover the bigger distance with a symmetrical cable.

 

[ognolman]

The guitar cord is shielded.  The wire distance I was talking about is not the distance from the pick up to the preamp, but the total distance of the traces in the preamp.

Yes, I understood this.  I was just thinking out loud, I guess.  So am I wrong about the amplifying noise thing?

JBD

 

[Patrick from Davis]

Prolly not.